Abstract: According to the coking mechanism and the actual operation of a 2.2 Mt/a catalytic cracking unit in a petrochemical enterprise, it is considered that the atomization effect of feedstock is not good and the contact of oil agent is not uniform, the existence of non-vaporized oil is the main cause of coking in riser and affects the coking in follow-up system. When the temperature is lower than the dew point temperature of the heavy component, the droplets will condense, the heavy oil droplets and the catalyst will stick to the wall or inner component in the stationary region and the region where the oil and gas flow changes greatly, and then the dehydrogenation and condensation reaction will gradually solidify and accumulate to form large coke blocks. The process optimization measures of strict control of raw material quality, control of reaction depth, reduction of slurry refining amount, improvement of catalyst performance and increase of reaction steam injection amount were adopted, and some technical improvement measures were taken, such as optimizing degassing tank, setting up middle pressure anticoking steam ring, and optimizing cyclone separator, etc. The results showed that the coking of the reaction system was effectively alleviated, and the safe long-term operation of the device was ensured.

Key words: deep catalytic cracking, coking, leg, settler, slurry